Apparatus for inductive longitudinal or helical seam welding of tubular metallic workpieces

ABSTRACT

An apparatus for inductive longitudinal or helical seam welding of tubular metallic workpieces has a tube roller device for advancing a tubular workpiece shaped from a metal band so as to have a V-shaped gap between the butt faces of the band. The roller device also applies pressure to the workpiece for joining the butt faces. The apparatus has a longitudinal inductor and a second ring-shaped inductor disposed between the longitudinal inductor and the location whereat the butt faces are joined. The longitudinal inductor is located above the V-shaped gap in partially overlapping relation to the gap edges and has longitudinal iron yoke sheet metal members in proximity to the edges. The longitudinal inductor has two component parts one of which overlaps one of the gap edges and the other part overlaps the opposite edge of the V-shaped gap. Current supply conductors form respective windings for the two conductor parts. Each of the windings is arranged above a portion of the tube surface corresponding adjacent to the gap edge overlapped by the corresponding one of the component inductor parts.

United States Patent Schaier [54] APPARATUS FOR INDUCTIVE LONGITUDINALOR HELICAL SEAM WELDING 0F TUBULAR METALLIC WORKPIECES [72] Inventor:Hans Schaier, Erlangen, Germany [73] Assignee: SiemensAktiengesellschait, Berlin and Munich, Germany [22] Filed: March 10,1971 [21] Appl.No.: 122,889

[30] Foreign Application Priority Data March 13, 1970 Germany ..P 20 11915.7 Y

[52] US. Cl. ..219/8.5, 219/1053, 219/10.79

[51] Int. Cl. ..H05b 9/02 [58] Field of Search.... ..2l9/8.5, 10.53,10.75, 10.79,

[56] References Cited UNITED STATES PATENTS 3,248,512 4/1966 Sommer.219/s. 5 2,938,993 5/1960 Rudd ..2l9/8.5 x 3,242,300 3/1966 Osbom.......219/s.5 3,5 2,470 2/1971 Bobart ..219/10.61 x

[151 1 3,701,871 1451 Oct. 31, 1972 Primary Examiner-J. V. TruheAssistant Examiner-B. A. Reynolds AttorneyCurt M. Avery, Arthur E.Wilfond, Herbert L. Lerner and Daniel J. Tick [s7] ABSTRACT An apparatusfor inductive longitudinal or. helical seam welding of tubular metallicworkpieces has a tube roller device for advancing a tubular workpieceshaped from a metal band so as to have a V-shaped gap between the buttfaces of the band. The roller device also applies pressure to theworkpiece for joining the butt faces. The apparatus has a longitudinalinductor and a second ring-shaped inductor disposed between thelongitudinal inductor and the location whereat the butt faces arejoined. The longitudinal inductor is located above the V-shaped gap inpartially overlapping relation to the gap edges and has longitudinaliron yoke sheet metal members in proximity to the edges. Thelongitudinal inductor has two component parts one of which overlaps oneof the gap edges and-the other part overlaps the opposite edge of theV-shaped gap. Current supply conductors form respective windings for thetwo conductor parts. Each of the windings is arranged above a portion ofthe tube surface corresponding adjacent to the gap edge overlapped bythe corresponding one of the component inductor parts.

4 Claims, 2 Drawing Figures APPARATUS FOR INDUCTIVE LONGITUDINAL ORHELICAL SEAM WELDING OF TUBULAR METALLIC WORKPIECES I My inventionrelates'to an apparatus for inductive longitudinal or helical'seamwelding of tubular metallic workpieces wherein a roller device isprovided for advancing the tubular member. The tubular workpiece isshaped from a metal band so as to have a V-shaped gap between thebuttfaces of the band. The'rollerfdevice also applies pressure to theworkpiece for joining the butt faces. The apparatus includes alongitudinal inductorand a second ring shaped inductor disposed betweenthe longitudinal inductor and the location whereat the butt faces arejoined. The longitudinal inductor is located over the V-shaped gap 50that the outer edges of the gap are practically, overlapped thereby..lnthe region of the gap the longitudinal inductor is provided with ironyoke sheet metal members.

An apparatus of this type is known for example from U.S. Pat. No.3,248,512. With such an apparatus the welding temperature forthe-welding operation at the location where the butt faces are joined isdeveloped cordingly, with the apparatus of the invention time congapswhich correspond to tubes of low and medium with the ring-shapedinductor at joining location. With the inductive preheater, the edgeeffect is reduced since the gap edges and the butting surfaces of the V-shaped gap are separately heated. However, it is a disadvantage thatwith the preheating of the gap edges, a greater temperature gradient.occurs between the butting faces and/or between the gap edges and theremaining metal band. The heat therefore flows rapidly away and there isformed at the butting edges only a small heat reserve. Therewith thereexists the danger of a seam weld hardening which in general must betreated with a subsequent heat treatment.

Accordingly, it is an object of my invention to provide a tube weldingapparatus of the. aforementioned type wherein weld seam hardening isprevented.

' According to a feature of my invention I provide a seam weldingapparatus having a longitudinal inductor which includes two componentparts. One of the parts overlaps one of the edges of the V-shaped gapand the other component part overlaps the other edge of the gap. Thecurrent supply conductors form respective windings for the componentparts. Each of thewindings is arranged above a portion of the skinregion adjacent to the gap edge overlapped by the corresponding one ofthecomponent parts.

Preferably and according to a further feature of the invention the twocomponent parts are arranged one behind the other in a directionsubstantially parallel to the longitudinal axis of the tubularworkpiece, the component parts being located to one side of the locationwhereat the butt faces of the tubular conductor are joined. Thecomponent part closest to the joining location is shorter than the othercomponent part.

. By means of the windings which is provided for each component part ofthe longitudinal conductor, there a're'respective ring currents inducedin the skin regions of the tube at both sides of the V-shaped gap whichacts to heat the surface of the tube. Since the magnitude of the heatcurrent, in addition to the unchangeable material conditioned factors,is dependent on the temper'ature difference, the heat runoff from thebutting edges into the metal band is thereby" reduced and the heatstored at the gap edges is increased. Therefore, hardening of the weldseam no longer occurs. Ac-

quality. In addition, by means of the division of the longitudinalinductor into parts with the respectively 'different lengths there isobtained the result that the temperature of both gap edges are heated tothe same degree when the tube advances into the welding zone whereat thetube is-heated by the ring-shaped inductor to the welding temperature.

The apparatus of the invention also has advantages with respect toapparatus of the kind described in German printed Pat. application No.1,099,664. In this known apparatus the inductive preheater lies in theV-shaped gap. Accordingly, a heat store in the gap edges does not formwith this arrangement. In addition, the longitudinal inductor arrangedin the gap is technically difficult to obtain. I The invention will nowbe described with reference to the drawings wherein;

FIG. 1 illustrates a schematic diagram of a seam welding apparatusaccording to the invention; and FIG. 2 is a view,'.partially in section,of the'apparatus of FIG. 1 taken along line II--II. I

FIG. 1 illustrates a tube welding apparatus according I to the inventionin plan view. A tube 1 preformed from a metal band is moved forward andpressed together by the pressure rollers 2. A V-shaped gap 4 is definedby the butting edges 3. The butting edges 3 are heated to the weldingtemperature and the apertaining butt surfaces are pressed together bypressure rollers, 2 at the contact point 5 to form a welded seam 6.

A ring-shaped inductor 7 is provided for developing 7, a ring current isdeveloped in preformed tube 1 which heats the upper and low edges ofthegap very.

' ring-shaped inductor 7. The field of the longitudinal inductor 8penetrates into the gap 4 and heats also the middle regions of thebutting surfaces to a temperature which lies below the weldingtemperature. Thereby, in

the shortest possible time and with a small expenditure of highfrequency energy, the butting edges and butting surfaces are brought tothe intermediate state betweenthe solid state and liquid state and apress welding is obtained with substantially increased welding speed.Consequently, the production of the apparatus is substantiallyincreased. I

The longitudinal inductor 8 comprises two component parts 9 and 10 whichare arranged one behind edge 3b of the gap 4 laying opposite the edge3a. The

- two parts 9 and 10 are joined by a conductor member. 13 so that theentire longitudinal inductor 8 has the form of an off-set conductor.

The two parts 9 and 10 are so arranged over the respective gap edges 3aand 3b so that they preferably extend with half their width over the gap4. The field of the component parts 9 and 10 extends into the gap 4 andheats the butting surfaces in addition to the edges 3a and 3b. Thecomponent part 10 positioned next to the welding location 5 is shorterthan the part 9 placed further distant from the location 5. In this waythere is obtained the effect that the temperature of the edges andbutting surfaces are approximately of the same magnitude when the tubeenters the region of the ringshaped inductor 7. From FIG. 1 it isdirectly apparent that the longitudinal inductor is in a simple mannerfitted to the gap geometry because of the division of the longitudinalinductor 8 into the two component parts 9 and 10. For example, with thelongitudinal inductor of the invention, efficaciously permits heatingthe small V-shaped gaps which are associated for example with tubeshaving a small diameter and, as in most instances, a small wallthickness. I t

It should be noted that the inductor of the invention is not limited tothe illustrated form, for example, the component parts 9 and 10 can bepositioned partially or entirely next to each other.

With the current supply means 140 and 14b for this longitudinal inductor8, each component part 9 and 10 is provided with windings 15 and 16respectively. These windings 15 and 16 lie over a part of the skinregions of the preformed tube 1 which border on gap edges 3a and 3brespectively. With these windings l5 and 16 a that is, a subsequent heattreatment of the welded tube is prevented. 7

FIG. 2 illustrates a section of the apparatus of FIG. 1 taken along linelI Il. In order not to obscure the view, the ring-shaped inductor 7 andthe pressure rollers 2 are omitted from FIG. 2.

FIG. 2 illustrates the configuration of the current supply means 14a and14b. In addition, FIG. 2 shows the spacing or separation of the windings15 and 16 from the skin regions of the preformed tube 1. With thisseparation, the coupling and thereby the intensity of the ring currentis adjustable in the skin regions of the tube 1. The coupling distanceis thereby in a last instance responsible for the heating of thesurface, and therefore, for the heat stored in the edges 3a and 3b andthe appertaining butting faces. The coupling distance is determined independence upon: the nature of the material, the tube diameter, thethickness of the tube wall, and the welding speed.

The longitudinal inductor 8 as well as the ringshaped inductor 7 areprovided with a cooling channel 17 for water cooling. The coolingchannel 7 of the longitudinal inductor 8 is illustrated in FIG. 2 andthe cooling channel 17 of the ring-shaped inductor 7 is illustrated inFIG. 1. The cooling channels of the longitudinal inductor 8 as well asthe cooling channels of the ring-shaped inductor 7 can be joinedtogether as a sine c lin h l. g1 w i ietfig i tl g tion has beendescribed by means of a specific example and in a specific embodiment, Ido not wish to be limited thereto, for obvious modifications will occurto those skilled in the art according to the spirit and scope of theinvention.

' Iclaim:

1. Apparatus for inductive seam welding of tubular metallic workpieces,comprising a tube roller device for advancing a tubular workpiece shapedfrom a metal band so as to have a V-shaped gap between the butt faces ofthe band, said roller device applying pressure to the workpiece forjoining said butt faces, a first longitudinal inductor, a secondring-shaped inductor disposed between said longitudinal inductor and thelocation whereat said butt faces are jointed, said longitudinal inductorbeing located above said V-shaped gap in partially overlapping relationto the gap edges, said longitudinal inductor having iron yoke sheetmetal members in proximity of said edges; said longitudinal inductorcomprising two component parts located abovesaid V-shaped gap, one ofsaid two parts overlapping one of said gap edges, said other part'overlapping the opposite edge of said V-shaped gap and both of saidparts being interconnected by a conductor member located above saidV-shaped gap; current supply conductors which form respectivewindings'for said two component parts, each of said windings beingarranged above a portion of the tube surface adjacent to the gap edgeoverlapped by the corresponding one of said component parts.

2. Apparatus according to claim 1, saidcomponent parts overlapping saidgap to an extent corresponding to approximately half the width of saidparts.

3. Apparatus according to claim 1, said longitudinal inductor having acooling channel disposed therein.

4. Apparatus for inductive seam welding of tubular metallic workpieces,comprising a tube roller device for advancing a tubular workpiece shapedfrom a metal band so as to have a V-shaped gap-between the butt faces ofthe band, said roller device applying pressure to the workpiece forjoining said butt faces, a first longitudinal inductor, a secondring-shaped inductor disposed between said longitudinal inductor and the10- cationwhereat said butt faces are joined, said longitudinal inductorbeing located above said V-shaped gap in partially overlapping relationto the gap edges, said longitudinal inductor having iron yoke sheetmetal members in proximity of said edges; said longitudinal inductorcomprising two component parts, one of said two parts overlapping one ofsaid gap edges, said other part overlapping the opposite edge of saidV-shaped gap; current supply conductors which form respective windingsfor said two component parts, each of said windings being arranged abovea portion of the tube surface adjacent the gap edge overlapped by thecorresponding one of said component parts, said component parts beingarranged one behind the other so as to extend in a directionsubstantially parallel to the longitudinal axis of the tube, saidcomponent parts being located to one side'of said location whereat saidbutt

1. Apparatus for inductive seam welding of tubular metallic workpieces,comprising a tube roller device for advancing a tubular workpiece shapedfrom a metal band so as to have a Vshaped gap between the butt faces ofthe band, said roller device applying pressure to the workpiece forjoining said butt faces, a first longitudinal inductor, a secondring-shaped inductor disposed between said longitudinal inductor and thelocation whereat said butt faces are jointed, said longitudinal inductorbeing located above said V-shaped gap in partially overlapping relationto the gap edges, said longitudinal inductor having iron yoke sheetmetal members in proximity of said edges; said longitudinal inductorcomprising two component parts located above said V-shaped gap, one ofsaid two parts overlapping one of said gap edges, said other partoverlapping the opposite edge of said V-shaped gap and both of saidparts being interconnected by a conductor member located above saidV-shaped gap; current supply conductors which form respective windingsfor said two component parts, each of said windings being arranged abovea portion of the tube surface adjacent to the gap edge overlapped by thecorresponding one of said component parts.
 2. Apparatus according toclaim 1, said component parts overlapping said gap to an extentcorresponding to approximately half the width of said parts. 3.Apparatus according to claim 1, said longitudinal inductor having acooling channel disposed therein.
 4. Apparatus for inductive seamwelding of tubular metallic workpieces, comprising a tube roller devicefor advancing a tubular workpiece shaped from a metal band so as to havea V-shaped gap between the butt faces of the band, said roller deviceapplying pressure to the workpiece for joining said butt faces, a firstlongitudinal inductor, a second ring-shaped inductor disposed betweensaid longitudinal inductor and the location whereat said butt faces arejoined, said longitudinal inductor being located above said V-shaped gapin partially overlapping relation to the gap edges, said longitudinalinductor having iron yoke sheet metal members in proximity of saidedges; said longitudinal inductor comprising two component parts, one ofsaid two parts overlapping one of said gap edges, said other partoverlapping the opposite edge of said V-shaped gap; current supplyconductors which form respective windings for said two component parts,each of said windings being arranged above a portion of the tube surfaceadjacent the gap edge overlapped by the corresponding one of saidcomponent parts, said component parts being arranged one behind theother so as to extend in a direction substantially parallel to thelongitudinal axis of the tube, said component parts being located to oneside of said location whereat said butt faces are joined, the componentpart lying closet to said location being shorter than the othercomponent part.